Questions: The graph below represents the solution set of which inequality?
x^2 - 2x - 8 < 0
x^2 + 2x - 8 < 0
x^2 - 2x - 8 > 0
x^2 + 2x - 8 > 0
Transcript text: The graph below represents the solution set of which inequality?
$x^{2}-2 x-8<0$
$x^{2}+2 x-8<0$
$x^{2}-2 x-8>0$
$x^{2}+2 x-8>0$
Solution
Solution Steps
Step 1: Identify the intervals on the graph
The graph shows the solution set for the inequality. The solution set is the interval between -2 and 4, not including -2 and 4.
Step 2: Determine the roots of the quadratic inequalities
The roots of the quadratic inequalities are the points where the quadratic expression equals zero. We need to find which quadratic inequality has roots at -2 and 4.
Step 3: Test the inequalities
\(x^2 - 2x - 8 < 0\)
Factor: \((x - 4)(x + 2) < 0\)
Roots: \(x = 4\) and \(x = -2\)
The inequality is satisfied between the roots, i.e., \(-2 < x < 4\).
\(x^2 + 2x - 8 < 0\)
Factor: \((x - 2)(x + 4) < 0\)
Roots: \(x = -4\) and \(x = 2\)
The inequality is satisfied between the roots, i.e., \(-4 < x < 2\).
\(x^2 - 2x - 8 > 0\)
Factor: \((x - 4)(x + 2) > 0\)
The inequality is satisfied outside the roots, i.e., \(x < -2\) or \(x > 4\).
\(x^2 + 2x - 8 > 0\)
Factor: \((x - 2)(x + 4) > 0\)
The inequality is satisfied outside the roots, i.e., \(x < -4\) or \(x > 2\).
Final Answer
The inequality that matches the solution set on the graph is:
\[ x^2 - 2x - 8 < 0 \]